iFit/sw_nvect

 determines the best normal vector for the set of vectors

 [n collinear] = SW_NVECT(S, {epsilon})

 S           Array of column vectors, dimensions are [3 N].
 epsilon     Upper limit of the collinearity and the lower limit of
             coplanarity. Default value is 0.1. If epsilon = 1 the
             function returns n vector closest to the collinear direction,
             if epsilon = 2, n will be closest to the normal of the spin
             plane.

 n           Vector parallel to the collinear spin direction or
             perpendicular to the plane of the spins in planar structures,
             dimensions are [1 3].

 collinear   If true, the set of vectors are collinear, then n is parallel to the
             input vectors.